Field of the Invention
The present invention concerns a method to determine a magnetic resonance (MR) relaxation time, in particular a T2* relaxation time, in the heart muscle in a magnetic resonance examination.
Description of the Prior Art
A determination of the MR relaxation times—for example a relaxation time T2*, a T1 relaxation time or a T2 relaxation time—is helpful in a number of magnetic resonance examinations.
For example, a determination of the transversal relaxation time T2* is appropriate in magnetic resonance measurements (MR) for a diagnosis of thalassemia. Thalassemia is a genetically caused abnormality in hemoglobin production. Left untreated, patients can possibly suffer from anemia that is accompanied by an increased iron concentration in the heart muscle (myocardium). Evidence of the iron concentration in the myocardium is primarily relevant for therapy. A change in the iron concentration results in a shortening of the T2* time in a magnetic resonance measurement. Exact quantitative information about the T2* time is therefore desirable.
According to the prior art, a quantification of the T2* relaxation time in the myocardium can be achieved using a multi-gradient echo measurement with suitably selected echo times TE1 . . . TEn. At first, however, only individual images (frames) with varying contrast result from this measurement, from which the T2* time is still not quantitatively apparent. Therefore the images of the multi-gradient echo measurement are evaluated with an interactive auxiliary program (for example CMRtools). The goal of the additional evaluation is to establish a region of interest (ROI) of an optimally standardized (reference) tissue region in the left ventricle. A region from the ventricular septum is typically selected as a standardized tissue region. The signal intensity of this tissue region is then approximated as a function of the echo time to an exponential fit, i.e. with the use of an adapted exponential function. The T2* time for this tissue region results from the multiple images of the multi-gradient echo measurement.
This interactive evaluation of the images of the multi-gradient echo measurement requires additional auxiliary programs as well as an interaction of the user or treating physician, and is therefore time-consuming, costly and/or even error prone given an operating error.
According to the prior art, a quantitative determination of additional MR relaxation times in the heart muscle—for example a determination of T1 or T2 relaxation time—is likewise complicated.